Apparatus for annealing



Patented June 9, 1942 FFICE I APPARATUS FOR ANNEALING .narom Olcott Shepard, Pittsburgh, Pa., assignor to United Engineering and Foundry Company,

Pittsburgh, Pa.

Application May 27, 1940, Serial N0. 337,372 I 11 Claims.

This invention relates to apparatus for heat treating of metal and more particularly for the heat treatment of aluminum strip and material of like character;

In heat treating certain metals it is desirable to heat the metal to a temperature which is nearly as high as the temperature 'at which the tensile strength of the metal practically disappears. Duralumin, for example, loses substantially all of its tensile strength by the time it reaches a temperature of 966 F., but to increase its ultimate strength it should be heated to a temperature from about 932 to 950 F. and then quenched'in a liquid. Due to the loss in tensile strength of such material at such high temperatures, difficulty has "been encountered in heat treating it in the usual manner in continuously moving strip form, which has many advantages, because the tension that has heretofore been exerted on it is quite likely to tear it apart. I

It is among the objects of this invention to provide apparatus for the heat treatment of continuously moving metal strip at any'desired temperature without danger of it separating, which apparatus is compact and which'obtains the maximum heating effect for its size.

treating apparatus and 2 is a vertical section taken on the line II-- II of Fig. 1.

Referring to the drawing, continuous metal 7 strip I is unwound from a coil (not shown) and In accordance with this invention continuously it is immediately cooled in order to re-establish' its tensile strength so that it will not separate when appreciable tension is placed on it again. For thi purpose the cooling means engages the strip substantially at the point at which it leaves the carrier in the heating chamber. Preferably, the carrier comprises a heated drum to'which the strip is fed at substantially its lowest point and which it leaves after it has traveled more than three-fourths of the way around the circumference of the drum. The cooling means most suitably "is a roll which holds the strip led over a roller 2 into one end of an insulated furnace or heatingchamber 3 through a small opening 4 therein. Extending through the side' walls of this chamber is a stationary horizontal shaft 6 on which a hollow strip-carrying drum I is journaled. The bearings for the drum may be cooled by water pipes 5 in any suitable manner. Rigidly connected to one side of the drum, as shown in Fig. 2, is a shaft-encircling sleeve 8 that projects out of the chamber and has] mounted on its outer end a sprocket 9 or other suitable means for rotating the drum from any convenient power supply. The metal strip I is drawn into the chamber by the frictional engagement therewith of the drivenfdrum and a roll ll between which the strip extends and which serve as'pinch rolls for this purpose. Be-

tween furnace inlet] and the roll the strip travels between guide plates l3'over rollers 14.

The strip is carried through the heating chain-i her to an outlejt'opening IS in its Opposite end by the drum around which the strip extends from roll H In initially threading the strip I j gagement with it at the point where rollji is 10- i cated, noftension is placed on the portion of the strip supported by the drum ahead of that point.

This permits the supported portion of the strip to be heated to a temperatureat' which the strip would otherwise tear apart. In order to obtain as long a heating zone as possible without placing the strip under appreciable tension, roll II is located at the lowest point of thedrum and the heating zone for the strip extends from this point around the drum for more than threeagainst the drum and around which it is led away from the drum to a tank containing the desired cooling liquid. I

The preferred embodiment of apparatus constructed in accordance with my invention is ilfourths of its circumference tooutlet ii of the chamber.

The desired temperatureis obtained in the furnace partly by heating the drum by electric resistors I], connected by suitable controls, not

I shown, to a source of power L1 L2, supported close to its innersurface by an annular band I8 concentric therewith and rigidly connected to shaft 6. The rest of the heat is furnished by electric resistors l9, connected by suitable controls, not shown, to a source of power L3 L4, mounted on the inner surface of an outer annular band 20 encircling the drum a short distance therefrom and secured to the side walls of the furnace. This outer band is broken at the chamber outlet and at the bottom where roll H is located. If desired, the inner surfaces oi guide plates l3 may also be provided with elec tric resistors 2| for preheating the strip before it reaches the drum, but of course the temperature of the strip is not raised sufliciently during such preheating to materially aiiect its tensile strength.

Another feature of this invention is that the tensile strength of the strip is increased as it leavesthe drum so that the increased tension which is exerted on the strip before it reaches the cooling bath in a tank 26 will not tear it. Accordingly, journaled in the entry end of the tank, which is disposed outside of the furnace below its outlet I6, is a pair of driven pinch rolls 2'! one of which is entirely submerged in the bath and the other of which is partly submerged but has its upper portion extending above the tank and through furnace outlet l6 nearly into engagement with the drum. In fact, the upper roll holds the strip against the drum because it is disposed below the central horizontal plane of the drum and between diametrically opposite points on its circumference in that plane. The hot strip would otherwise hang straight down from one of those points and its weight would cause it to pull apart. Although the pinch rolls are driven at the same peripheral speed as the drum so that they will not pull the strip, the strip is subjected to some strain as it is led away from the drum down around the upper pinch roll and between the two rolls in the tank. However, the strip is strengthened so that it can withstand this strain because the upper roll is cooled by the liquid in the tank and thereby starts to reduce the temperature of the strip as soon as it engages it, which is at the point at which it leaves the drum. To hasten this cooling, nozzles 28 are positioned adjacent the opposite surface of the strip for spraying a cooling liquid thereon before it reaches the bite of the pinch rolls. From these rolls the strip loops down through the cooling liquid in the tank and passes out of it over a roller 29 at its delivery end and to driven pinch rolls 3!. After the strip has been dried it can be recoiled.

To control the size of the loop in the tank so that it will not disappear and pull the strip from the pinch rolls, photoelectric cells: 32- are mounted at opposite sides of the tank. If the loop in the tank starts to shorten, it permits the light beam to be established between the cells and this controls an electric circuit in well known manner which slows down pinch rolls 3| so that the size of the loop will beincreased. As soon -as the loop inrreases suificiently to cause the light beam to be broken between the cells, the pinch roll speed will again increase.

and described what I now consider to represent its best embodiment. However; I desire to have it understood that, within the scope of the ap pended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. Heat treating apparatus comprising a heating chamber, means for carrying thin continuous metal strip therethrough under substantially no tension, means for heating the strip supported by said carrying means to a temperature at which its tensile strength is reduced to almost zero, and a cooling roll cooperating with said carrying means and around which the strip is ledaway from the carrying means, said roll .engaging the strip at the point at which it is delivered from said carrying means.

2. Heat treating apparatus comprising a heating chamber, a drum journaled on a horizontal axis therein for carrying continuous metal strip therethrough under substantially no tension,

means for heating the strip carried by the drum, and a driven cooling roll cooperating with said drum and journaled adjacent the delivery side of the drum and around which the strip is led away therefrom, the roll being spaced from the drum a distance substantially equal to the thickness of the strip.

3. Heat treating apparatus comprising a heating chamber, means for carrying continuous metal strip therethrough under substantially no tension, means for heating the strip supported by said carrying means to a temperature at which its tensile strength is reduced to almost zero, a cooling tank disposed adjacent the delivery point of said carrying means, a pair of driven pinch rolls cooperating with said carrying means associated with said tank for feeding the strip between them after it leaves the carrying means, one of said rolls engaging the strip at the point at which it leaves the carrying means, a pair of driven'plnch rolls for receiving the strip from the tank, said strip forming a loop in the means for heating the strip carried by the drum,

It will thus be seen that with my invention continuous metal strip can be heat treated without danger of its being pulled apart if it is heated to a temperature at which it can not withstand appreciable tension, and that this heat treatment is accomplished in relatively small, compact and simple apparatus.

According to the provisions of the patent statutes, I have explained the principle and mode of operation of my invention and have illustrated and a cooling roll journaled adjacent the delivery side of the drum and around which the strip is led away from the drum, the strip engaging both the drum and the roll substantially at the pass between them.

5. Heat treating apparatus comprising a heating chamber, a drum journaled on a horizontal axis therein for carrying continuous metal strip therethrough under substantially no tension, means for heating the strip carried by the drum, and a cooling roll journaled adjacent the delivery side of the drum and holding the strip against the drum between its lowest point and its central horizontal plane and around which the strip is led away from the drum.

6. Heat treating apparatus comprising a heating chamber, a drum journaled on a horizontal axis therein for carrying continuous metal strip therethrough under substantially no tension, means in the chamber for delivering the strip to the drum at approximately its lowest point,

means for heating the strip carried by the drum, and a cooling roll journaled closely adjacent the delivery side of the drum less than 45 below its central horizontal plane and around which the strip is led away from the drum.

7. Heat treating apparatus comprising a heating chamber, a driven drum journaled on a horizontal axis therein for carrying continuous metal strip therethrough under substantially no tension, 2, roll journaled at the bottom of the drum and up around which the strip extends to the bite between the drum and roll, means for heating-the strip carried by the drum, and means in close proximity to the point at which the strip leaves the drum for cooling the strip before the tension thereon becomes material.

8. Heat treating apparatus comprising a heating chamber, a driven drum journaled on a horizontal axis therein for carrying continuous metal strip therethrough under substantially no tension, 9. roll journaled at the bottom' of the drum and up around which the strip extends to the bite between the drum and roll, means for guiding the strip to the bottom of said roll, means for heating the strip carried by the drum, and means in close proximity to the point at which the strip leaves the drum for cooling the strip before the tension thereon becomes material.

9. Heat treating apparatus comprising a heating chamber, a driven drum journaled on a horizontal axis therein for carrying continuous metal strip therethrough under substantially no .ten-

sion, a roll journaled at the bottom of the drum and up around which the strip extends to the bite between the drum and roll, means for guiding the strip to the bottom of said roll, means for preheating the strip before it reaches said roll, means for heating the strip carried by the drum, and means in close proximity to the point at which the strip leaves the drum for cooling the strip before the tension thereon becomes material.

10. Heat treating apparatus comprising a heating chamber, a drum journaled on a horizontal axis therein for carrying continuous metal strip therethrough under substantially no tension, annularly disposed heating means mounted inside of said drum, heating means encircling said drum, and means in close proximity to the point at which the strip leaves the drum for cooling the strip before the tension thereon becomes material.

11. Heat treating apparatus comprising a heating chamber, a drum journaled on a horizontal axis therein for carrying continuous metal strip therethrough, 'annularly disposed heating means mounted inside of said drum, heating means encircling said drum, and means in the chamber for delivering the strip to the drum at approximately its lowest point, said strip engaging the drum for at least three-quarters of its circumference.

HAROLD O. SHEPARD. 

